This thread has piqued my interest because I have been playing around with an extending Kamm-rear spoiler idea. The critical downstream rear angles could always benefit to a long-tail configuration. The idea is very similar to reconfigurable/extending airplane wing flaps. The move-able wing extend & become flush/fixed to the fastback surface & additional wingtips deploy downwards to clean up some side flow. I've considered these add. tips to deploy outside the rear light assembly but would compromise the safety equipment. The wingtips always could be made w/ clear polycarbonate to passed safety reqs. Lower speeds & parking maneuvers needs retracting the wings. 'Active' wing flap angles become too complicated.
Also another idea, a model specific (Prius 2010) rear wheel covers extend to very clean flows sharply detaching at the bottom & rear edges...
